Hitherto, there have been mainly produced two types of golf balls. The one is a solid golf ball, such as a two-piece golf ball or three-piece golf ball, and the other is a thread wound golf ball. The solid golf ball, when compared with the thread wound golf ball, has better durability and better flight performance because of a larger initial velocity at the time of hitting and longer flight distance. Therefore, the solid golf ball is generally approved or utilized by many golfers, particularly amateur golfers. With regard to enhancement of flight distance, the development of the golf ball has mainly focused on solid golf balls rather than thread wound golf balls.
On the other hand, the solid golf ball exhibits hard and poor shot feel at the time of hitting. It has been known that the flight distance is largely affected by the rebound characteristics of the solid golf ball. Recently, in order to improve the shot feel of the solid golf ball, it has been attempted to soften the core of the solid golf ball to reduce the hardness of the golf ball. However, there is the drawback that the rebound characteristics of the golf ball are degraded and the flight performance is reduced, because of the softening of the core.
These performances are generally governed by two factors, that is the surface hardness of the core and the deformation amount of the core. When the surface hardness is larger, the deformation amount is reduced and the rebound characteristics are enhanced, but the shot feel is poor. On the other hand, when the surface hardness is smaller, the deformation amount is decreased and the shot feel is enhanced, but the rebound characteristics are degraded. Therefore, it is very difficult to improve both flight distance and shot feel of the conventional, solid golf ball having a solid core.